使用jquery验证插件（servlet和jsp）检查用户名可用性

Question

我使用jquery验证器插件来验证我的注册表单。但是，当我尝试检查用户名是否在数据库中时，它不起作用。任何人都可以帮助看看我的代码，让我知道我做错了什么？即使用户名不在数据库中，它也始终显示用户已存在。

我尝试了

中的方法

  

    

jQuery Validate remote method usage to check if username already exists和JQuery Remote Validation not displaying Error

  

但它仍然无效。

我的注册jquery功能：

   $().ready(function() {

        $.validator.addMethod('uniqueUsername', function(value) {
            $.ajax({
                url: 'http://localhost:8080/TBS-war/RegisterServlet.java',
                type: 'POST',
                async: false,
                contentType: 'application/json',
                dataType: 'json'

            });
        });

        //Validate signup form on keyup and submit
        $("#registrationForm").validate({
            // Set rules
            rules: {
                username: {
                    required: true,
                    uniqueUsername: true
                    /*remote: {
                        url: "http://localhost:8080/TBS-war/RegisterServlet.java",
                        type: "post",
                        contentType: "application/json",
                        data: {
                            'username': $('#username').val()
                        }
                    }*/
                },
                password: {
                    required: true
                },
                confirmPassword: {
                    required: true,
                    equalTo: "#password"
                },
                contact: {
                    required: true
                },
                email: {
                    required: true,
                    email: true
                },
                address: {
                    required: true
            }},

            // Set messages
            messages: {
                username: {
                    required: "* This field is required",
                    uniqueUsername: "* User already exist"
                    //remote: "* User already exist"
                },
                password: {
                    required: "* This field is required"
                },
                confirmPassword: {
                    required: "* This field is required",
                    equalTo: "* Please enter the same password as above"
                },
                contact: {
                    required: "* This field is required"
                },
                email: {
                    required: "* This field is required",
                    email: "* Please enter a valid email"
                },
                address: {
                    required: "* This field is required"
            }},

我的servlet文件：

@EJB
private TBSManagerBeanRemote tBSManagerBean;


    @Override
    protected void doPost(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        response.setContentType("application/json");

        PrintWriter out = response.getWriter();
        JSONObject json = new JSONObject();
        String username = request.getParameter("username");

        if (tBSManagerBean.userExist(username)) {
            out.print("{\"valid\" : false }");
            json.put("valid", false);
            System.out.println("false");
        }
        else {
            out.print("{\"valid\" : true }");
            json.put("valid", true);
            System.out.println("true");
        }
    }